The IPCC recently released the policy-maker’s summary (SREX-SPM) on extreme weather and climate events. The background for this report is a larger report that is due to be published in the near future, and one gets a taste of this in the ‘wordle‘ figure below. By the way, the phrase ‘ET’ in this context does not refer ‘extra-terrestrial’, and ‘AL’ is not a person, but these refer to the way of citing many scholars: ‘et al.‘
There are two new papers in Nature this week that go right to the heart of the conversation about extreme events and their potential relationship to climate change. This is a complex issue, and one not well-suited to soundbite quotes and headlines, and so we’ll try and give a flavour of what the issues are and what new directions these new papers are pointing towards.
[Read more…] about Going to extremes
Guest commentary by Ron Miller, NASA GISS
Several studies have shown that hurricane activity is generally reduced during years when there is a thick aerosol haze over the subtropical Atlantic. The haze is comprised mainly of soil particles, stripped by wind erosion from the barren ground over the Sahara and Sahel. These particles are lifted into the atmosphere and carried by the Trade winds as far as the Caribbean and Amazon basin. Plumes of dust streaming off the African coast are easily recognized in satellite imagery, and were even described by Charles Darwin during his voyage on the Beagle.
By Rasmus Benestad & Michael Mann
Just as Typhoon Nargis has reminded us of the destructive power of tropical cyclones (with its horrible death toll in Burma–around 100,000 according to the UN), a new paper by Knutson et al in the latest issue of the journal Nature Geosciences purports to project a reduction in Atlantic hurricane activity (principally the ‘frequency’ but also integrated measures of powerfulness).
The close timing of the Knutson et al and Typhoon Nargis is of course coincidental. But the study has been accorded the unprecedented privilege (that is, for a climate change article published during the past 7 years) of a NOAA press conference. What’s the difference this time? Well, for one thing, the title of the paper: “Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions” (emphasis added).
Guest Commentary from Urs Neu
When discussing the influence of anthropogenic global warming on hurricane or tropical cyclone (TC) frequency and intensity (see e.g. here, here, and here), it is important to examine observed past trends. As with all climate variables, the hurricane record becomes increasingly uncertain when we go back in time. However, the hurricane record has some peculiarities: hurricanes are highly confined structures, so you have to be at the right place at the right time to observe them. Secondly, hurricanes spend most of their life in the open oceans, i.e. in regions where there are very few people and no fixed observations. This means that the reliability of the long-term hurricane record is dependent on who was measuring them, and how, at any given time. The implementation of new observation methods, for example, might have altered the quality of the record considerably. But how much? This crucial question has been widely discussed in the recent scientific literature (e.g. Chang and Guo 2007, Holland and Webster 2007, Kossin et al. 2007, Landsea 2007, Mann et al. 2007). Where do we stand at the moment? This post will concentrate on the North Atlantic, which has the longest record.
If you are a RealClimate regular, you are undoubtedly aware of our ongoing interest in the developments in the scientific understanding of potential hurricane-climate change linkages. This is an area of the science where a substantial body of significant new research has emerged even since RealClimate’s inception in late 2004. The scientific research in this area, and the media frenzy and political theatrics that have inescapably followed it, are thoughtfully placed in a broader historical context in a fascinating new book by Chris Mooney entitled Storm World: Hurricanes, Politics, and the Battle over Global Warming. Anyone who is at all interested in the scientific history that has led to our current understanding of Hurricanes and their potential linkages with climate change, will find this book a page turner. The book is a nice complement to Kerry Emanuel’s recent book Divine Wind: The History and Science of Hurricanes (which too is so readable that it lies on our coffee table). Mooney in a sense picks up where Emanuel’s left off. Like Emanuel, he explores the history of the science. But he uses this historical context, and his studies of the personalities of key actors, to explore how the current scientific debate can be traced back to a rift that has emerged over many decades between distinct communities of atmospheric scientists.
[Read more…] about Storm World: A Review
Michael Mann and Gavin Schmidt
A recent paper by Vecchi and Soden (preprint) published in the journal Geophysical Research Letters has been widely touted in the news (and some egregiously bad editorials), and the blogosphere as suggesting that increased vertical wind shear associated with tropical circulation changes may offset any tendencies for increased hurricane activity in the tropical Atlantic due to warming oceans. Some have even gone so far as to state that this study proves that recent trends in hurricane activity are part of a natural cycle. Most of this is just ‘spin’ (pun intended), but as usual, the real story is a little more nuanced.
[Read more…] about Hurricane Spin
Michael Mann and Gavin Schmidt
[update 3/20/07: The New York Times has run a short letter from us w/ a link to RealClimate for more info (scroll down to 5th letter; the 2nd letter from James McCarthy of Harvard is quite good too, as are some of the others).]
The first rule when criticizing popular science presentations for inaccuracies should be to double check any ‘facts’ you use. It is rather ironic then that William Broad’s latest piece on Al Gore plays just as loose with them as he accuses Gore of doing.
We criticized William Broad previously (Broadly Misleading) for a piece that misrepresented the scientific understanding of the factors that drive climate change over millions of years, systematically understating the scientifically-established role of greenhouse gases, and over-stating the role of natural factors including those as speculative as cosmic rays (see our recent discussion here). In this piece, Broad attempts to discredit Gore’s “An Inconvenient Truth” by exaggerating the legitimate, but minor, criticisms of his treatment of the science by experts on climate science, and presenting specious or unsubstantiated criticisms by a small number of the usual, well-known contrarians who wouldn’t agree even if Gore read aloud from the latest IPCC report.
[Read more…] about Broad Irony
The big problem with much of the discussions about trends in hurricane activity is that the databases that everyone is working from are known to have significant inhomogeneities due to changes in observing practice and technology over the years. So it’s not surprising that a new re-analysis (Kossin et al, published yesterday) has been generating significant interest and controversy among the hurricane research community (see e.g. Prometheus or Chris Mooney). However, rather than this study being taken for what it is – a preliminary and useful attempt to make homogeneous a part of the data (1983 to 2005) – it is unfortunately being treated as if it was the definitive last word. We’ve often made the point that single papers are not generally the breakthroughs that are sometimes implied in press releases or commentary sites and this case is a good example of that.
[Read more…] about Hurricane Heat
It has now become all too common. Peculiar weather precipitates immediate blame on global warming by some, and equally immediate pronouncements by others (curiously, quite often the National Oceanic and Atmospheric Administration in recent years) that global warming can’t possibly be to blame. The reality, as we’ve often remarked here before, is that absolute statements of neither sort are scientifically defensible. Meteorological anomalies cannot be purely attributed to deterministic factors, let alone any one specific such factor (e.g. either global warming or a hypothetical long-term climate oscillation).
Lets consider the latest such example. In an odd repeat of last year (the ‘groundhog day’ analogy growing ever more appropriate), we find ourselves well into the meteorological Northern Hemisphere winter (Dec-Feb) with little evidence over large parts of the country (most noteably the eastern and central U.S.) that it ever really began. Unsurprisingly, numerous news stories have popped up asking whether global warming might be to blame. Almost as if on cue, representatives from NOAA’s National Weather Service have been dispatched to tell us that the event e.g. “has absolutely nothing to do with global warming”, but instead is entirely due to the impact of the current El Nino event.
[Update 1/9/07: NOAA coincidentally has announced today that 2006 was officially the warmest year on record for the U.S.]
[Update 2/11/08: It got bumped to second place. ]
[Read more…] about El Nino, Global Warming, and Anomalous U.S. Winter Warmth